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Abstract:

A light-emitting sheet which does not cause failures such as a short
circuit without causing dielectric breakdown at the end of element at
applying a voltage and which is able to realize stable driving is
provided. Specifically, A light-emitting sheet comprising a first
electrode, a second electrode, and a light-emitting layer disposed
between the first and the second electrodes, wherein the first electrode
and/or the second electrode disposed on and under the periphery of the
light-emitting layer are cut to form a non-conductive portion being
electrically disconnected with a circuit for applying a voltage to the
light-emitting sheet, and as seen from a vertical direction to the plane
of the light-emitting sheet, the non-conductive portion formed from the
first electrode or the non-conductive portion formed from the second
electrode surrounds the light-emitting layer, or the non-conductive
portion formed from the first electrode and the non-conductive portion
formed from the second electrode are apparently connected to each other
and surrounds the light-emitting layer.

Claims:

1. A light-emitting sheet, comprising: a first electrode; a second
electrode: and a light-emitting layer disposed between the first and the
second electrodes, wherein at least one electrode selected from the group
consisting of the first electrode and the second electrode is disposed on
and under a periphery of the light-emitting layer and comprises a
non-conductive portion, which is electrically disconnected from a circuit
which applies a voltage to the light-emitting sheet, and when viewing the
light emitting sheet from a vertical direction to a plane of the
light-emitting sheet, the non-conductive portion of the first electrode
or the non-conductive portion of the second electrode surrounds the
light-emitting layer, or the non-conductive portion of the first
electrode and the non-conductive portion of the second electrode are
apparently connected to each other and surround the light-emitting layer.

2. The light-emitting sheet according to claim 1, wherein the
non-conductive portion of the at least one electrode is obtained by a
process comprising cutting the at least one electrode with a laser.

3. The light-emitting sheet of claim 1, wherein a minimum value of a
creepage distance between a conductive portion of the first electrode and
a conductive portion of the second electrode, which are electrically
connected to each other, is 2 mm or more.

4. The light-emitting sheet of claim 1, further comprising: a dielectric
layer between the first electrode and the light-emitting layer.

5. The light-emitting sheet of claim 1, further comprising: a dielectric
layer between the second electrode and the light-emitting layer.

6. The light-emitting sheet of claim 1, wherein the first electrode
comprises a non-conductive portion, which is electrically disconnected
from a circuit, and when viewing the light emitting sheet from a vertical
direction to a plane of the light-emitting sheet, the non-conductive
portion of the first electrode surrounds the light-emitting layer.

7. The light-emitting sheet of claim 6, wherein the non-conductive
portion of the first electrode is obtained by a process comprising
cutting the first electrode with a laser.

8. The light-emitting sheet of claim 7, wherein a minimum value of a
creepage distance between a conductive portion of the first electrode and
a conductive portion of the second electrode, which are electrically
connected to each other, is 2.5 mm or more.

9. The light-emitting sheet of claim 8, further comprising: a dielectric
layer between the first electrode and the light-emitting layer.

10. The light-emitting sheet of claim 8, further comprising: a dielectric
layer between the second electrode and the light-emitting layer.

11. The light-emitting sheet of claim 1, wherein the second electrode
comprises a non-conductive portion, which is electrically disconnected
from a circuit, and when viewing the light emitting sheet from a vertical
direction to a plane of the light-emitting sheet, the non-conductive
portion of the second electrode surrounds the light-emitting layer.

12. The light-emitting sheet of claim 11, wherein the non-conductive
portion of the second electrode is obtained by a process comprising
cutting the second electrode with a laser.

13. The light-emitting sheet of claim 12, wherein a minimum value of a
creepage distance between a conductive portion of the first electrode and
a conductive portion of the second electrode, which are electrically
connected to each other, is 2.5 mm or more.

14. The light-emitting sheet of claim 13, further comprising: a
dielectric layer between the first electrode and the light-emitting
layer.

15. The light-emitting sheet of claim 13, further comprising: a
dielectric layer between the second electrode and the light-emitting
layer.

16. The light-emitting sheet of claim 1, wherein the first and the second
electrode each comprise a non-conductive portion, which are electrically
disconnected from a circuit, and when viewing the light emitting sheet
from a vertical direction to a plane of the light-emitting sheet, the
non-conductive portion of the first and second electrodes are apparently
connected to each other and surround the light-emitting layer.

17. The light-emitting sheet of claim 16, wherein the non-conductive
portion of the first electrode and the non-conductive portion of the
second electrode are obtained by a process comprising cutting the first
and second electrode with a laser, respectively.

18. The light-emitting sheet of claim 17, wherein a minimum value of a
creepage distance between a conductive portion of the first electrode and
a conductive portion of the second electrode, which are electrically
connected to each other, is 2.5 mm or more.

19. The light-emitting sheet of claim 18, further comprising: a
dielectric layer between the first electrode and the light-emitting
layer.

20. The light-emitting sheet of claim 18, further comprising: a
dielectric layer between the second electrode and the light-emitting
layer.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a light-emitting sheet. In more
detail, the present invention relates to a light-emitting sheet which
does not cause failures such as a short circuit and which is able to
realize stable driving.

BACKGROUND ART

[0002] As functional elements in the electric/electronic field or the
optical field, there is known an electroluminescent element capable of
emitting light by applying a voltage. In general, this electroluminescent
element can be broadly classified into an inorganic electroluminescent
element having a light-emitting layer which contains an inorganic
electroluminescent material (hereinafter referred to as "inorganic EL
element") and an organic electroluminescent element having a
light-emitting layer which contains an organic electroluminescent
material (hereinafter referred to as "organic EL element").

[0003] In comparison with the organic EL device, the inorganic EL device
is hard to emit light with high luminance, it has such an advantage that
not only it is excellent in long-term stability, but it stably causes
light emission even under a severe condition such as a high temperature.
For that reason, in order to utilize it in fields where weather
resistance, heat resistance, long-term stability, or the like is
required, studies regarding the inorganic EL element are being continued.

[0004] An inorganic EL element which is driven by an alternating current
source can be formed on paper or a polymer film by utilizing a printing
technology, and it forms a market as an illumination device in which
flexibility is required. As such an inorganic EL element, there is known
an electroluminescent element in which an insulating layer and a
light-emitting layer are formed on a back-side electrode, a transparent
electrode is provided thereon, and the top and bottom thereof are covered
with a hygroscopic film. The light-emitting layer is printed by means of
screen printing or the like (see, for example, Patent Document 1).
However, such a technique requires a lot of manufacturing processes. For
that reason, as a method capable of achieving mass production, there is
known a method of inexpensively manufacturing an inorganic EL element by
means of roll printing and lamination (see, for example, Patent Document
2).

[0007] In inorganic EL elements manufactured by the conventional methods,
because the upper and lower are come to close one another at the end of
element, dielectric breakdown possibly occurs by applying a voltage, so
failures such as a short circuit are frequently caused.

[0008] To solve the above problem, the present invention provides a
light-emitting sheet having high dielectric strength properties and
capable of suppressing failures such as a short circuit.

Means for Solving the Problem

[0009] That is, the present invention relates to the following [1] to [4].

[1] A light-emitting sheet comprising a first electrode, a second
electrode, and a light-emitting layer disposed between the first and the
second electrodes, wherein

[0010] the first electrode and/or the second electrode disposed on and
under the periphery of the light-emitting layer are cut to form a
non-conductive portion being electrically disconnected with a circuit for
applying a voltage to the light-emitting sheet, and as seen from a
vertical direction to the plane of the light-emitting sheet, the
non-conductive portion formed from the first electrode or the
non-conductive portion formed from the second electrode surrounds the
light-emitting layer, or the non-conductive portion formed from the first
electrode and the non-conductive portion formed from the second electrode
are apparently connected to each other and surrounds the light-emitting
layer.

[2] The light-emitting sheet according to [1], wherein the first
electrode and/or the second electrode are cut with a laser. [3] The
light-emitting sheet according to [1] or [2], wherein a minimum value of
a creepage distance between a conductive portion of the first electrode
and a conductive portion of the second electrode being electrically
connected to each other is 2 mm or more by cutting the electrode or
electrodes. [4] The light-emitting sheet according to any one of [1] to
[3], comprising a dielectric layer between the first electrode or the
second electrode and the light-emitting layer.

EFFECT OF THE INVENTION

[0011] According to the present invention, is possible to provide a
light-emitting sheet in which dielectric breakdown will not occur at the
ends of the element by applying a voltage, failures such as a short
circuit will not be caused, and will be stable to drive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a diagram showing a light-emitting sheet 1 comprising a
light-emitting layer disposed between a first electrode on a first
substrate and a second electrode on a second substrate, as seen from the
second electrode surface side.

[0013] FIG. 2 is a lateral sectional view of the light-emitting sheet 1.

[0014] FIG. 3 is a diagram showing a light-emitting sheet (light-emitting
sheet 2) obtained by cutting the second electrode of the light-emitting
sheet 1 into a U-shape with a laser beam machine.

[0015] FIG. 4 is a diagram showing a light-emitting sheet (light-emitting
sheet 2) obtained by cutting the first electrode of the light-emitting
sheet 1 linearly along a vertical direction with a laser beam machine.

[0016] FIG. 5 is a lateral sectional view of the light-emitting sheet 2.

[0017] FIG. 6 is a vertical sectional view of the light-emitting sheet 2.

[0018]FIG. 7 is a diagram explaining a position of the "periphery" of a
light-emitting layer.

MODES FOR CARRYING OUT THE INVENTION

[0019] The light-emitting sheet of the invention relates to a
light-emitting sheet comprising a first electrode, a second electrode,
and a light-emitting layer disposed between the first and the second
electrodes, wherein the first electrode and/or the second electrode
disposed on and under the periphery of the light-emitting layer
(hereinafter referred to as "light-emitting layer periphery") is cut to
form a non-conductive portion being electrically disconnected with a
circuit for applying a voltage to the light-emitting sheet. Here, the
term "light-emitting layer periphery" is a side surface site of the
light-emitting layer which does not face any of the first electrode and
the second electrode, and in FIG. 7 showing a lateral sectional view of a
light-emitting sheet, the light-emitting layer periphery means a side
surface site 7 of a light-emitting layer 3 disposed between a first
electrode substrate 1 and a second electrode substrate 2. A planar shape
of the light-emitting sheet is not particularly limited, and it may be
any of a quadrilateral-shape such as a square, a rectangle, a trapezoid,
a rhombus or the like, a triangle, a circle, an ellipse, and a star.
Hereinafter, a light-emitting sheet in which the first electrode is a
cathode, the second electrode is an anode, the first substrate side is a
back, and the second substrate is a front is explained as an example, but
it should not be limited thereto.

(Substrate for Electrode)

[0020] It is preferred that the first electrode (cathode) and the second
electrode (anode) is formed on an each substrate (hereinafter, a
substrate for the first electrode and a substrate for the second
electrode are referred to as "first substrate" and "second substrate",
respectively; and a laminate of the first electrode on the first
substrate and a laminate of the second electrode on the second substrate
are referred to as "first electrode substrate" and "second electrode
substrate", respectively). The first substrate and the second substrate
are not particularly limited, for example, glass plates or plastic films
can be used. From the point of view that they have flexibility and are
able to reduce the weight, plastic films are preferred. As the plastic
films, films which may not permeate moisture or whose moisture
permeability is extremely low are preferred. In addition, it is important
that the second substrate has transparency.

[0021] As materials such a plastic films, polyesters and polyamides are
preferred from the viewpoints of costs and multiplicity of uses. Examples
of the polyester include polyethylene terephthalate, polybutylene
terephthalate, polyethylene naphthalate, polyarylates. Also, examples of
the polyamide include wholly aromatic polyamides, nylon 6, nylon 66,
nylon copolymers.

[0022] Although a thickness of the substrate to be used is not
particularly limited, it is generally from 1 to 1,000 μm, preferably
from 5 to 500 μm, and from the viewpoint of practicality, more
preferably from 10 to 200 μm.

[0023] In addition, it is not particularly needed that the first substrate
is transparent.

[0024] Although the second substrate may be either colorless transparent
or colored transparent, it is preferred that the second substrate is
colorless transparent from the viewpoint of not scattering or attenuating
light emitted from a light-emitting layer as described below.

[0025] Also, in each of the first substrate and the second substrate, a
moisture barrier layer (gas barrier layer) can be provided on its front
or back surface as necessary. As a material of the moisture barrier layer
(gas barrier layer), inorganic materials such as silicon nitride and
silicon oxide are suitably used. The moisture barrier layer (gas barrier
layer) can be, for example, formed by a high-frequency sputtering method
or the like.

[First Electrode; Cathode]

[0026] The first electrode (cathode) in the light-emitting sheet of the
present invention is not particularly limited as far as it has a function
as a cathode, and it can be appropriately selected from known cathodes
according to an application of the light-emitting sheet.

[0027] Examples of a material of the first electrode include metals,
alloys, metal oxides, organic conductive compounds, and mixtures thereof.

[0028] Specific examples of the material of the first electrode include
gold, silver, lead, aluminum, indium, ytterbium, and alloys or mixture of
such a metal and an alkali metal or an alkaline earth metal; organic
conductive polymers such as polyaniline, polythiophene, and polypyrrole.
These materials may be used alone or as a combination of two or more
thereof. Among these materials, it is preferred that its work function is
not more than 4.5 eV.

[0029] Among these materials, a material mainly composed of aluminum is
preferred in regard to its excellent stability. The material mainly
composed of aluminum as referred to herein means aluminum alone, or an
alloy or a mixture of aluminum and about 0.01 to 10% by mass of an alkali
metal or an alkaline earth metal (for example, a lithium-aluminum alloy,
a magnesium-aluminum alloy, and the like).

[0030] Since the formation method of the first electrode is not
particularly limited, it is possible to form the first electrode by a
known method. For example, in view of the properties of a material, the
first electrode can be formed on the first substrate by a method
appropriately selected from among a wet process such as a printing method
and a coating method, a physical process such as a vacuum vapor
deposition method, a sputtering method, an ion plating method, a chemical
process such as a CVD method (chemical vapor deposition method) and a
plasma CVD method, and a method of laminating metal foils.

[0031] For example, in the case of selecting metals such as aluminum as
the material of the first electrode, the first electrode can be formed by
a method such as sputtering one or two or more kinds of metal on the
substrate simultaneously or successively, or laminating metal foils.

[0032] Although a thickness of the first electrode can be appropriately
selected depending on the material and not be generalized, it is
generally in the range of 10 nm to 50 μm, preferably 20 nm to 20
μm, and more preferably 50 nm to 15 μm. It is noted that this first
electrode may be transparent or be opaque. A surface resistivity of the
first electrode is preferably not more than 103Ω/quadrature,
and more preferably not more than 102Ω/quadrature. The
surface resistivity is a value determined by a method described in the
Examples.

[Second Electrode; Anode]

[0033] The second electrode (anode) in the light-emitting sheet of the
present invention is not particularly limited as far as it has a function
as an anode and transparency, and it can be appropriately selected from
known anodes according to an application of the light-emitting sheet.

[0034] Examples of the material of the second electrode include metals,
alloys, metal oxides, organic conductive compounds, and mixtures thereof.

[0035] Specific examples of the material of the second electrode include
metal oxides such as tin oxide, antimony-doped tin oxide (ATO),
fluorine-doped tin oxide zinc oxide, indium oxide, indium tin oxide
(ITO), and indium zinc oxide (IZO); metals such as gold, silver,
chromium, and nickel; mixture or laminate of these metal oxides and
metals; organic conductive polymers such as polyaniline, polythiophene,
and polypyrrole. Among these materials, it is preferred that its work
function is 4.0 eV or more, and from the viewpoint of its high
transparency, ITO is particularly preferred.

[0036] The second electrode can be formed by a known method. For example,
in view of the properties of material, the second electrode can be formed
on the second substrate by a method appropriately selected from a wet
process such as a printing method and a coating method, a physical
process such as a vacuum vapor deposition method, a sputtering method,
and an ion plating method, a chemical process such as CVD and a plasma
CVD method.

[0037] For example, in the case of selecting ITO as the material of the
second electrode, the second electrode can be formed by a method such as
direct current or high-frequency sputtering method, a vacuum vapor
deposition method, and an ion plating method. Also, in the case of
selecting an organic conductive compound as the material of the second
electrode, the second electrode can be formed by a wet film forming
method.

[0038] Although a thickness of the second electrode can be appropriately
selected depending on the material and not be generalized, it is normally
in the range of 10 to 1,000 nm, preferably 20 to 500 nm, and more
preferably 50 to 200 nm.

[0039] A surface resistivity of the second electrode is preferably not
more than 102Ω/quadrature, and more preferably not more than
102Ω/quadrature. The surface resistivity is a value
determined by a method described in the Examples.

[0040] Though the second electrode may be colorless transparent or colored
transparent, it is preferably colorless transparent. In addition, in
order to allow the escape produced light from the second electrode side,
a transmittance of the laminate of the second substrate and the second
electrode is preferably 60% or more, and more preferably 70% or more. The
transmittance is a value determined by a method described in the
Examples.

[Light Emitting Layer]

[0041] In the light-emitting sheet of the present invention, the
light-emitting layer can be, for example, formed by coating a
light-emitting composition on the first electrode or the second
electrode, or a dielectric layer as described below. Also, the
light-emitting layer may be formed by coating a light-emitting
composition on a release film and then transferring it onto the first
electrode or the second electrode, or the dielectric layer.

[0042] It is possible to use the light-emitting composition which contains
an electroluminescent material and a matrix resin. The electroluminescent
material and the matrix resin will be sequentially described below.

(Electroluminescent Material)

[0043] As the electroluminescent material, any of an inorganic
electroluminescent material and an organic electroluminescent material
can be used. From the viewpoint of an application of the light-emitting
sheet of the present invention, it is preferred to use an inorganic
electroluminescent material which is excellent in long-term stability.

Inorganic Electroluminescent Material

[0044] Examples of the inorganic electroluminescent material include those
in which a base material of zinc sulfide (ZnS) is doped with copper,
manganese, terbium fluoride, samarium fluoride or thulium fluoride as a
main luminescent material, i.e. ZnS:Cu, ZnS:Mn, ZnS:TbF3, ZnS:SmF3 and
ZnS:TmF3; a base material of calcium sulfide (CaS) is doped with europium
as a main luminescent material, i.e. CaS:Eu; a base material of strontium
sulfide (SrS) is doped with cerium as a main luminescent material, i.e.
SrS:Ce; and a base material of alkaline earth-based calcium sulfide such
as CaCa2S4 and SrCa2S4 is doped with a transition
metal such as manganese or a rare earth element such as europium, cerium,
and terbium as a main luminescent material.

[0046] Furthermore, Examples of the inorganic electroluminescent material
include oxide light-emitting materials composed of Sc2O3 doped
with a rare earth element such as Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy,
Ho, Er, Tm, Yb, and Lu, exclusive of Sc. The rare earth element used for
doping is preferably Ce, Sm, Eu, Tb, or Tm. Depending on the kind of the
rare earth element, the inorganic electroluminescent material emits
yellow light, red light which has a longer wavelength than yellow light,
or green or blue light which has a shorter wavelength than yellow light.

[0047] In the present invention, these inorganic electroluminescent
materials may be used alone, or a combination of two or more thereof, if
desired.

Organic Electroluminescent Material

[0048] As the organic electroluminescent material, any of low-molecular
weight material and high-molecular weight material can be used. Also, any
of fluorescent materials and phosphorescent materials can be used.

[0051] In the present invention, as the organic electroluminescent
materials, one of the low-molecular weight materials and high-molecular
weight materials may be used, or two or more thereof may be used in
combination.

[0052] In the case where the light-emitting layer is made of an organic
electroluminescent material, it is preferred to form a hole
injection/transport layer on the anode side of the light-emitting layer
and an electron injection/transport layer on the cathode side thereof,
respectively.

[0053] While a content of the electroluminescent material in the
light-emitting layer varies according to the inorganic material or the
organic material, in the case of the inorganic material, from the
viewpoints of balance between light emission properties and economy and
the like, in general, the content is preferably in the range of 20 to 900
parts by mass, more preferably 30 to 700 parts by mass, and still more
preferably 40 to 500 parts by mass based on 100 parts by mass of a matrix
resin as described below.

(Matrix Resin)

[0054] Examples of the matrix resin contained in the light-emitting
composition include polyesters such as polyethylene terephthalate,
polybutylene terephthalate, and polyester-based thermoplastic elastomers;
polyurethane and polyurethane-based thermoplastic elastomers; polystyrene
and polystyrene-based thermoplastic elastomers; polyvinyl chloride;
polyolefins such as polypropylene, and polyolefin-based thermoplastic
elastomers; silicone based resins; acrylic resins; and acrylic urethane
resins. Among these materials, those having tackiness at ambient
temperature are preferred. Using a resin having tackiness at ambient
temperature, it is possible to bond the light-emitting layer to the
electrode or the dielectric layer on application of pressure. As the
resin having tackiness, acrylic resins are preferred.

[0055] Examples of acrylic resins include copolymers of a (meth) acrylic
ester having from 1 to 20 carbon atoms in alkyl group and a monomer
optionally having a functional group such as a carboxyl group and other
monomer, namely (meth)acrylic ester copolymers.

[0056] Here, examples of the (meth)acrylic ester having from to 20 carbon
atoms in alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate,
propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl
(meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate,
myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate.
These materials may be used alone, or two or more may be used in
combination.

[0057] A weight average molecular weight of the (meth)acrylic ester
copolymer is preferably 300,000 or more, and more preferably 400,000 to
1,000,000.

[0058] To the light-emitting composition, additive such as a crosslinking
agent, an antioxidant, an ultraviolet absorbing agent, an infrared
absorbing agent, a pigment, and a fluorescent material may be optionally
added.

[0059] A coating method of the light-emitting composition is not
particularly limited, and a conventionally known method such as knife
coating, roll coating, bar coating, blade coating, die coating, and
gravure coating may be applied.

[0060] A thickness of the light-emitting layer obtained in this way is
generally 0.1 to 100 μm, preferably 5 to 90 μm, and more preferably
20 to 80 μm, from the viewpoints of a luminance of the light-emitting
sheet and laminating properties with respect to other layer.

[Dielectric Layer]

[0061] In the light-emitting sheet of the present invention, a dielectric
layer can be disposed between the first electrode and the light-emitting
layer and/or between the light-emitting layer and the second electrode.

[0062] As a material for forming this dielectric layer, materials having a
high dielectric constant are preferred. Examples thereof include
inorganic materials such as SiO2, BaTiO3, SiON,
Al2O3, TiO2, Si3N4, SiAlON, Y2O3,
Sm2O3, Ta2O5, BaTa2O3, PbNb2O3,
Sr(Zr,Ti)O3, SrTiO3, PbTiO3, HfO3, and Sb-containing
SnO2 (ATO); and organic materials such as polyethylene,
polypropylene, polystyrene, epoxy resins, and cyanoacetyl cellulose.
These materials may be used alone, or two or more thereof may be used in
combination.

[0063] In the case where the dielectric layer is present between the
light-emitting layer and the second electrode, the dielectric layer is
required to be transparent. Therefore, among the above materials,
inorganic materials such as SiO2, Al2O3, Si3N4,
Y2O3, Ta2O5, BaTa2O3, SrTiO3, and
PbTiO3 are preferred. In the case where the dielectric layer is
present between the first electrode and the light-emitting layer, it is
not particularly needed that the dielectric layer is transparent.

[0064] The dielectric layer can be, for example, formed by coating a
dispersion obtained by uniformly dispersing the material for forming a
dielectric layer in a suitable binder according to a conventionally known
coating method such as spraying, knife coating, roll coating, bar
coating, blade coating, die coating, and gravure coating, or by using an
extruder. Although the binder is not particularly limited, for example,
the same materials as those in the above matrix resin of the
light-emitting composition can be used. It is noted that in the case of
the organic material, it is possible to coat the material without using a
binder.

[0065] In the case of driving the light-emitting sheet of the present
invention with an alternating current, when an electrical conductivity of
the light-emitting layer is too high so that it is difficult to apply a
sufficient voltage to the light-emitting layer, or when dielectric
breakdown may be occurred due to an over current, the dielectric layer
exhibits an effect for controlling such a matter. From the viewpoint of
exhibiting the above effect, in general, a thickness of the dielectric
layer is preferably 0.1 to 50 μm, and more preferably 10 to 50 μm.

[Light Emitting Sheet]

[0066] As described above, in the light-emitting sheet of the present
invention, the first electrode and/or the second electrode disposed on
and under the periphery of the light-emitting layer is cut to form a
non-conductive portion being electrically disconnected with a circuit for
applying a voltage to the light-emitting sheet (hereinafter referred to
simply as "electrically non-conductive state"). As shown in FIG. 5, "the
first electrode and/or the second electrode disposed on and under the
periphery of the light-emitting layer" as referred to herein means, in
the lateral sectional shape of the light-emitting layer, the position
which is located around a first electrode edge and/or a second electrode
edge disposed on and under a side surface site of the light-emitting
layer, namely the position corresponding to a laser cut section 4 or 4'
(a cut section will be described below).

[0067] In the light-emitting sheet of the present invention, as seen from
a vertical direction to the plane of the light-emitting sheet, the
non-conductive portion formed from the first electrode or the
non-conductive portion formed from the second electrode surrounds the
light-emitting layer, or the non-conductive portion formed from the first
electrode and the non-conductive portion formed from the second electrode
are apparently connected to each other and so surrounds the
light-emitting layer.

[0068] The non-conductive portion may be formed only in the first
electrode or the second electrode. In the case of a light-emitting sheet
having four sides, the first electrode substrate and the second electrode
substrate are projected in order to connect each of the first electrode
and the second electrode to a power source as shown in FIG. 2, it is
preferred that three sides of one of the electrodes (for example, the
second electrode) is cut into a U-shape, and the other electrode (for
example, the first electrode) corresponding to the remaining one side is
cut to form a non-conductive portion (see FIGS. 3 and 4). By cutting the
electrodes as below, a light-emitting sheet comprising a non-conductive
portion in which the first electrode and the second electrode each having
a substrate are easily connected with a power source is obtained.

(Cutting Condition of Electrode)

[0069] Although a method of cutting the electrode is not particularly
limited to, it is preferred to use a laser beam machine because of
ease-to-use. The laser beam machine is not particularly limited, examples
thereof include a YAG laser, a CO2 laser, an excimer laser, and a
femtosecond laser.

[0070] A laser output or a scanning rate may be appropriately regulated so
as to form a non-conductive section. As a standard, for example, in the
case of cutting the electrode from the side of electrode substrate, it is
generally preferred that a laser output is 30 to 80 W and a scanning rate
is 350 to 700 mm/s, and more preferred that a laser output is 30 to 80 W
and a scanning rate is 380 to 650 mm/s when the thickness of the
electrode substrate is in the range of 50 to 100 μm.

[0071] A cut section of the electrode may be located inside the end of the
light-emitting layer. However, in order to prevent a light-emitting area
being excessively small, the cut section is preferably 2 to 10 mm, more
preferably 3 to 8 mm, and still more preferably 4 to 6 mm from the end of
the electrode. Also, a part of the light-emitting layer may be cut. It is
noted that after cutting the electrode from the electrode side of the
electrode substrate, the light-emitting layer and the electrode may be
laminated.

[0072] From the viewpoint of preventing a short circuit, in general, a
cutting line width is preferably 10 μm or more. However, a short
circuit preventing ability does not alter even by widening the cutting
line width more than necessary, but the light-emitting area becomes
small. Therefore, the cutting line width is more preferably 10 to 200
μm, and still more preferably 20 to 180 μm.

[0073] In addition, a minimum value of a creepage distance between an edge
of the conductive section of the first electrode and an edge of the
conductive section of the second electrode, both of which is electrically
disconnected, is preferably 2 mm or more, and more preferably 2.5 mm or
more by cutting the electrode. The term "creepage distance" as described
herein means the shortest distance when a distance between any points of
an edge of the conductive section of the first electrode and an edge of
the conductive section of the second electrode is measured along the
surface of the light-emitting layer (in the case where the light-emitting
sheet has a dielectric layer, the surface of the dielectric layer is also
included). For example, in FIG. 5, the creepage distance is expressed by
a total distance of two arrows. It is noted that the creepage distance is
a value not taking into consideration a depth of the light-emitting layer
cut together at cutting the electrode.

[Producing Method of Light-Emitting Sheet]

[0074] An embodiment of the production of the light-emitting sheet of the
present invention is not particularly limited, so any method may be
adopted as far as a light-emitting sheet having the above constitution
can be obtained.

[0075] An example of the method for producing the light-emitting sheet of
the present invention include a method in which a first laminate and a
second laminate are made by the following process (1) or (2), then the
light-emitting layer side of the first laminate and the second electrode
side of the second laminate, or the first electrode side of the first
laminate and the light-emitting layer side of the second laminate are
bonded each other.

(1) A process of forming a first electrode and a light-emitting layer on
a first substrate in sequence to make a first laminate, and separately
forming a second electrode on a second substrate to make a second
laminate. (2) A process of forming a first electrode on a first substrate
to make a first laminate, and separately forming a second electrode and a
light-emitting layer on a second substrate in sequence to make a second
laminate.

[0076] In the above processes (1) and (2), the electrode may be cut at any
time, and timing of cut is not particularly limited. Examples thereof
include a method in which before forming the light-emitting layer, the
electrode is cut in advance to form a non-conductive portion; a method in
which after disposing the light-emitting layer between the first
electrode and the second electrode, the first electrode and/or the second
electrode is cut to form a non-conductive portion; and a method of a
combination of these.

[0077] Hereinafter, the constitutions of the first laminate and the second
laminate are conveniently expressed with symbols as follows. That is, the
first substrate and the second substrate are expressed by "1" and 2'',
respectively. And the first electrode and the second electrode are
expressed by "E1" and "E2", respectively. At the same time, the
light-emitting layer is expressed by "L", and the dielectric layer as
described below is expressed by "D" or "D'".

[0078] Then, the method through the above process (1), a laminate having a
constitution of 1-E1-L is obtained as the first laminate, and a
laminate having a constitution of 2-E2 is obtained as the second
laminate. By bonding these first laminate and second laminate with facing
L and E2 each other, a light-emitting sheet having a constitution of
1-E1-L-E2-2 is obtained.

[0079] In the method through the above process (2), a laminate having a
constitution of 1-E1 is obtained as the first laminate, and a
laminate having a constitution of 2-E2-L is obtained as the second
laminate. By bonding these first laminate and second laminate with facing
E1 and L each other, a light-emitting sheet having a constitution of
1-E1-L-E2 is obtained.

[0080] Further, making the first laminate and the second layer by anyone
of the following processes (3) to (12) and laminating the dielectric
layer side, light-emitting layer side or first electrode side of the
first laminate and the second electrode side, light-emitting layer side
or dielectric layer side of the second laminate by heat lamination, a
light-emitting sheet having a dielectric layer between the first
electrode or the second electrode and the light-emitting layer can also
be obtained. However, the present invention is not particularly limited
thereto.

(3) A process of forming a first electrode, a dielectric layer, and a
light-emitting layer in this order on a first substrate to make a first
laminate, and separately forming a second electrode on a second substrate
to make a second laminate. (4) A process of forming a first electrode and
a dielectric layer in sequence on a first substrate to make a first
laminate, and separately forming a second electrode and a light-emitting
layer in sequence on a second substrate to make a second laminate. (5) A
process of forming a first electrode on a first substrate to make a first
laminate, and separately forming a second electrode, a light-emitting
layer, and a dielectric layer in this order on a second substrate to make
a second laminate. (6) A process of forming a first electrode, a
light-emitting layer, and a dielectric layer in this order on a first
substrate to make a first laminate, and separately forming a second
electrode on a second substrate to make a second laminate. (7) A process
of forming a first electrode and a light-emitting layer in sequence on a
first substrate to make a first laminate, and separately forming a second
electrode and a dielectric layer in sequence on a second substrate to
make a second laminate. (8) A process of forming a first electrode on a
first substrate to make a first laminate, and separately forming a second
electrode, a dielectric layer, and a light-emitting layer in this order
on a second substrate to make a second laminate. (9) A process of forming
a first electrode, a dielectric layer, a light-emitting layer, and a
dielectric layer in this order on a first substrate to make a first
laminate, and separately forming a second electrode on a second substrate
to make a second laminate. (10) A process of forming a first electrode, a
dielectric layer, and a light-emitting layer in this order on a first
substrate to make a first laminate, and separately forming a second
electrode and a dielectric layer in sequence on a second substrate to
make a second laminate. (11) A process of forming a first electrode and a
dielectric layer in sequence on a first substrate to make a first
laminate, and separately forming a second electrode, a dielectric layer,
and a light-emitting layer in this order on a second substrate to make a
second laminate. (12) A process of forming a first electrode on a first
substrate to make a first laminate, and separately forming a second
electrode, a dielectric layer, a light-emitting layer, and a dielectric
layer in this order on a second substrate to make a second laminate.

[0081] It is noted that in the above processes (3) to (12), timing of
cutting the electrodes is not particularly limited. In addition, in the
above processes (9) to (12), the dielectric layer on the first electrode
side and the dielectric layer on the second electrode side may be the
same as or different from each other.

[0082] In the method through each of the above processes (1) to (12), the
constitution of the first laminate, the constitution of the second
laminate, and the constitution of the obtainable light-emitting sheet are
shown in Table 1.

[0083] From the viewpoint of improving the productivity of the
light-emitting sheet of the present invention, the light-emitting sheet
may be produced by a roll-to-roll process. The production of the
light-emitting sheet of the present invention by the roll-to-roll process
is a method in which unwinding a long electrode substrate wound-up into a
roll, then formation of a non-conductive section, formation of a
light-emitting layer, and bonding to an electrode substrate, and
optionally formation of a dielectric layer are performed, followed by
wound-up into a roll. Timing of forming the non-conductive section is not
particularly limited to, and it is possible to perform at an optional
stage.

[0084] In the case of adopting the roll-to-roll process, the first
electrode and/or the second electrode is cut on both two sides of the
light-emitting layer along a flow direction (vertical direction), and the
first electrode and/or the second electrode is also cut along width
direction (lateral direction).

[0085] The method for producing the light-emitting sheet of the present
invention by the roll-to-roll process is explained more specifically
below, but is not limited thereto.

(Roll-to-Roll Process (I))

[0086] (i) The long first electrode substrate (or the second electrode
substrate) wound-up into a roll is unwound, and the first electrode (or
the second electrode) is cut on two sides along flow direction to form a
non-conductive potion. The cut section is preferably 2 to 10 mm, more
preferably 3 to 8 mm, and still more preferably 4 to 6 mm from the end of
the first electrode (or the second electrode). It is noted that in this
case, from the viewpoint of performing the works in the following (ii)
and (iii) with ease, it is preferred to cut the electrode so as to remain
part of the substrate.

[0087] (ii) The light-emitting layer is formed on the first electrode
surface of the first electrode substrate (or the second electrode surface
of the second electrode substrate).

[0088] (iii) The second electrode substrate (or the first electrode
substrate) is formed on the light-emitting layer.

[0089] (iv) The first electrode and/or the second electrode are cut at any
position along width direction of the long light-emitting sheet to form a
non-conductive portion. In this case, considering an end of the electrode
in the size of the desired light-emitting sheet, the electrode is cut
preferably 2 to 10 mm, more preferably 3 to 8 mm, and still more
preferably 4 to 6 mm from the end of the electrode.

[0090] (v) The obtainable light-emitting sheet is wound-up into a roll.

(Roll-to-Roll System (II))

[0091] (i) The long first electrode substrate (or the second electrode
substrate) wound-up into a roll is unwound, and the light-emitting layer
is formed on the first electrode surface of the first electrode substrate
(or the second electrode surface of the second electrode substrate).

[0092] (ii) The second electrode (or the first electrode) is formed on the
light-emitting layer.

[0093] (iii) The first electrode (or the second electrode) is cut at any
position along width direction of the long light-emitting sheet to form a
non-conductive portion. In this case, considering an end of the electrode
in the size of the desired light-emitting sheet, the electrode is cut
preferably 2 to 10 mm, more preferably 3 to 8 mm, and still more
preferably 4 to 6 mm from the end of the electrode.

[0094] (iv) The first electrode and/or the second electrode are cut on two
sides along flow direction to form a non-conductive potion. The electrode
is cut preferably 2 to 10 mm, more preferably 3 to 8 mm, and still more
preferably 4 to 6 mm from the end of electrode.

[0095] (v) The obtainable light-emitting sheet is wound-up into a roll.

[0096] In the roll-to-roll processes (I) and (II), the above stages may be
continuously performed, or a method in which the light-emitting sheet is
once wound-up into a roll at each stage and then again unwound may be
adopted. Furthermore, a dielectric layer may be formed between each
electrode and the light-emitting layer as necessary.

[0097] The obtained light-emitting sheet as stated above is suppressed
with respect to dielectric breakdown at the time of applying a voltage
and does not cause failures such as a short circuit. Therefore, it is
excellent in prolonged stability as compared with conventional
light-emitting sheets.

EXAMPLES

[0098] Next, the present invention will be described in more detail with
reference to Examples based on the drawings, but it should be construed
that the present invention is not limited at all by these Examples.

[0099] It is noted that a weight average molecular weight of a
thermoplastic resin in the light-emitting layer used in each of the
Examples is a value which is determined by gel permeation chromatography
based on monodispersed polystyrene, and calculated in terms of
polystyrene standard. In addition, a surface resistivity of each of a
first electrode and a second electrode, and a transmittance of a second
electrode substrate were measured in the following manners.

[Measurement Method of Surface Resistivity of First Electrode and Second
Electrode]

[0100] A first electrode substrate and a second electrode substrate were
allowed to stand for 24 hours under a condition at 23° C. and a
relative humidity of 50% and then measured for a surface resistivity
under the same condition by using a surface resistivity meter (a product
name: R-127004, manufactured by ADVANTEST CORPORATION).

[Measurement Method of Transmittance of Second Electrode Substrate]

[0101] A transmittance of light having a wavelength of 550 nm was measured
from the electrode side by using an ultraviolet-visible-near infrared
spectrophotometer (a product name: UV-3101PC, manufactured by Shimadzu
Corporation).

[0102] It is noted that a first substrate, a first electrode, a second
substrate, a second electrode, a laminator, and a laser beam machine used
in each of the Examples are as follows.

[0105] A laminate having the first electrode laminated on the first
substrate is hereinafter referred to as "first electrode substrate". In
each of the Examples, a product name "ALPET (trademark) 12×50"
(manufactured by Ajiya Alminum KK) was used as the first electrode
substrate. A surface resistivity of the first electrode was found to be
0.5 Ω/quadrature.

[0108] A laminate having the second electrode laminated on the second
substrate is hereinafter referred to as "second electrode substrate". In
each of the Examples, a product name "MetalForce R-IT (E12)"
(manufactured by Nakai Industry Co., Ltd.) was used as the second
electrode substrate. A surface resistivity of the second electrode was
found to be 102Ω/quadrature, and a transmittance of light
having a wavelength of 550 nm from the second electrode substrate was
found to be 89%.

[0113] The obtained coating solution was applied to release surface of a
first release film (a product name: SP-PET3811, manufactured by Lintec
Corporation; referred to as "first release film" in each of the Examples)
with use of a knife coater so as to achieve a dry thickness of 55 μm,
and then heated and dried at 100° C. for 2 minutes to form a
light-emitting layer; and a second release film (a product name:
SP-PET3801, manufactured by Lintec Corporation; referred to as "second
release film" in each of the Examples) was laminated onto the surface of
the light-emitting layer, thereby obtaining a light-emitting layer having
the release film on the both surfaces thereof (referred to as
"light-emitting layer-containing sheet" in each of the Examples).

(Dielectric Layer)

[0114] A mixture of 100 parts by mass of an acrylic ester copolymer
composed of n-butyl acrylate and acrylic acid (n-butyl acrylate/acrylic
acid=90/10 (mass ratio), weight average molecular weight: 800,000), 100
parts by mass of titanium oxide (a product name: SZ Color #7030 White,
manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and 300
parts by mass of toluene as a solvent was thoroughly stirred, applied to
a release film (a product name: SP-PET3811, manufactured by Lintec
Corporation) so as to achieve a dry thickness of 10 μm and then dried
at 100° C. for 2 minutes, thereby forming a dielectric layer on
the release film (referred to as "dielectric layer-containing sheet" in
each of the Examples).

[0115] A dielectric strength test and a short circuit test of the
light-emitting sheet obtained in each of the Examples were performed in
the following manners.

[Dielectric Strength Test]

[0116] With respect to the light-emitting sheet obtained in each of the
Examples, a voltage at which dielectric breakdown occurred was measured
by using a dielectric strength analyzer (a product name: AC dielectric
strength tester 7220, manufactured by KEISOKU GIKEN Co., Ltd.) and
increasing an applied voltage in the range of 0 V to 1,000 V for one
minute at a current of 10 mA. The larger the voltage at which the
dielectric breakdown occurs, the more excellent the dielectric strength
properties are.

[Short Circuit Test]

[0117] The presence or absence of short circuit at the end of a
light-emitting sheet when the light-emitting sheet obtained in each of
the Examples was driven at AC 200 V and 2,000 Hz was visually confirmed.
It is noted that when a short circuit was generated, black spots were
confirmed immediately after driving.

Example 1

[0118] On a first electrode of a first electrode substrate 1 having a B4
size (364 mm broad by 257 mm long), a light-emitting layer 3 was
laminated by using a laminator while removing a second release film of a
light-emitting layer-containing sheet having dimension with 257 mm length
and 339 mm width. Then, a second electrode substrate 2 was laminated by
using a laminator in such a way that a second electrode surface of the
second electrode substrate 2 having a B4 size was contacted with the
light-emitting layer 3, while removing a first release film of the
light-emitting layer 3 laminated, thereby obtaining a light-emitting
sheet 1 as shown in FIGS. 1 and 2. It is noted that the shortest distance
from a left end of the first electrode substrate to a left end of the
light-emitting layer 3 (a width of a portion where the first electrode is
exposed), and the shortest distance from a right end of the second
electrode substrate to a right end of the light-emitting layer 3 (a width
of a portion where the second electrode is exposed) was made 25 mm,
respectively.

[0119] Subsequently, as shown in FIG. 3, the second electrode substrate
was cut 5 mm from edges along the edges of the second electrode substrate
2 of the light-emitting sheet 1 (laser cut sections 4 in FIG. 3) into a
U-shape by using a laser beam machine under a condition at a laser output
of 45 W and a scanning rate of 500 mm/s. It is noted that a width of the
laser cut section 4 was 85 μm and a cut depth thereof was 76 μm,
and the second electrode was cut to form a non-conductive portion 6 (see
FIGS. 5 and 6).

[0120] Furthermore, as shown in FIG. 4, the first electrode substrate was
cut 5 mm from edges along the edges of the first electrode substrate
(laser cut sections 4' in FIG. 4) by using a laser beam machine under a
condition at a laser output of 75 W and a scanning rate of 300 mm/s. It
is noted that a width of the laser cut sections 4' was 85 μm and a cut
depth thereof was 94 μm, and the first electrode was cut to form a
non-conductive portion 5 (see FIG. 5). The light-emitting sheet
comprising the non-conductive portions 5 and 6 (hereinafter referred to
as "light-emitting sheet A") was obtained in this way.

[0121] A minimum value of a creepage distance between the electrodes
(hereinafter referred to as "interelectrode creepage distance"), and the
results of dielectric strength test and short circuit test relating to
the obtained light-emitting sheet A are shown in Table 2.

Example 2

[0122] A light-emitting sheet (hereinafter referred to as "light-emitting
sheet B") was obtained in the same manner as in Example 1, except that
the first electrode substrate and the second electrode substrate were cut
2 mm from the edges of the electrode substrates, and the creepage
distance was shortened as shown in FIG. 2.

[0123] The interelectrode creepage distance and the results of dielectric
strength test and short circuit test relating to the obtained
light-emitting sheet B are shown in Table 2.

Example 3

[0124] A light-emitting sheet C was obtained in the same manner as in
Example 1, except that a dielectric layer having a 10 μm-thick was
formed between the first electrode and the light-emitting layer 3. That
is, a dielectric layer containing-sheet was laminated on the first
electrode surface of the first electrode substrate, the release film was
removed to form a laminate with the dielectric layer having a 10
μm-thick, and then the light-emitting layer 3 and the second electrode
substrate were laminated on the dielectric layer in a similar way of
Example 1, thereby obtaining the light-emitting sheet (hereinafter,
referred to as "the light-emitting sheet C).

[0125] The interelectrode creepage distance and the results of dielectric
strength test and short circuit test relating to the obtained
light-emitting sheet C are shown in Table 2.

Example 4

[0126] A light-emitting sheet (hereinafter referred to as "light-emitting
sheet D") was obtained in the same manner as in Example 1, except that
the first electrode substrate 1 was cut under a condition at laser output
of 38 W and a scanning rate of 500 mm/s. A width of a laser cut section
4' of the first electrode substrate 1 was 83 μm and a cut depth
thereof was 71 μm, and the first electrode was cut to form a
non-conductive portion 5.

[0127] The interelectrode creepage distance and the results of dielectric
strength test and short circuit test relating to the obtained
light-emitting sheet D are shown in Table 2.

Comparative Example 1

[0128] A light-emitting sheet (hereinafter referred to as "light-emitting
sheet E") was obtained in the same manner as in Example 1, except that a
non-conductive portion was not formed at all on the first electrode and
the second electrode.

[0129] The interelectrode creepage distance and the results of dielectric
strength test and short circuit test relating to the obtained
light-emitting sheet E are shown in Table 2.

Comparative Example 2

[0130] A light-emitting sheet (hereinafter referred to as "light-emitting
sheet F") was obtained in the same manner as in Example 1, except that a
non-conductive portion was formed only on the second electrode, and a
non-conductive portion was not formed on the first electrode.

[0131] The interelectrode creepage distance and the results of dielectric
strength test and short circuit test relating to the obtained
light-emitting sheet F are shown in Table 2.

[0132] From Table 2, the light-emitting sheet in which according to the
invention, the first electrode and/or the second electrode disposed on or
under the periphery of the light-emitting layer were cut to form the
non-conductive portion being electrically disconnected was high in the
dielectric strength property and free from the short circuit at driving
(see Examples 1 to 4).

[0133] On the other hand, in the light-emitting sheet in which the first
electrode and/or the second electrode disposed on and under the periphery
of the light-emitting layer were not cut at all (see Comparative Example
1) and the light-emitting sheet in which the first electrode and/or the
second electrode disposed on and under the periphery of the
light-emitting layer was not partially cut, and as seen from a vertical
direction to the plane of the light-emitting sheet, the non-conductive
portion formed from the first electrode and the non-conductive portion
formed from the second electrode did not apparently surround the
light-emitting layer (see Comparative Example 2), not only the dielectric
strength property was low, but the short circuit was generated at
driving.

INDUSTRIAL APPLICABILITY

[0134] The light-emitting sheet of the present invention is useful in
fields where weather resistance, heat resistance, long-term stability, or
the like is required, for example, backlight for advertising media
disposed on windows of commercial buildings and automobiles, decorating
media, security sheets, and the like.